US9494695B2 - Radiation monitor - Google Patents

Radiation monitor Download PDF

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US9494695B2
US9494695B2 US15/029,311 US201415029311A US9494695B2 US 9494695 B2 US9494695 B2 US 9494695B2 US 201415029311 A US201415029311 A US 201415029311A US 9494695 B2 US9494695 B2 US 9494695B2
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energy
rate
radiation
alert
low
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US20160252626A1 (en
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Kazuhiro Eguchi
Kenichi Moteki
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Mitsubishi Electric Corp
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Mitsubishi Electric Corp
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    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C17/00—Monitoring; Testing ; Maintaining
    • G21C17/002—Detection of leaks
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21C—NUCLEAR REACTORS
    • G21C17/00—Monitoring; Testing ; Maintaining
    • G21C17/003—Remote inspection of vessels, e.g. pressure vessels
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21D—NUCLEAR POWER PLANT
    • G21D1/00—Details of nuclear power plant
    • G21D1/006—Details of nuclear power plant primary side of steam generators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B37/00—Component parts or details of steam boilers
    • F22B37/02—Component parts or details of steam boilers applicable to more than one kind or type of steam boiler
    • F22B37/42—Applications, arrangements, or dispositions of alarm or automatic safety devices
    • F22B37/421—Arrangements for detecting leaks
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E30/00—Energy generation of nuclear origin
    • Y02E30/30—Nuclear fission reactors

Definitions

  • the present invention relates to a radiation monitor and particularly to a radiation monitor which confirms soundness of a steam generator in a pressurized water reactor plant.
  • This sensitive main steam pipe monitor includes: a radiation detector which is disposed close to a main steam pipe and detects a radiation to output an analog voltage pulse; and a count-rate measurement unit which receives the analog voltage pulse, discriminates the analog voltage pulse entering a high-energy window which is set to contain a photoelectric peak, a single-escape peak, and a double-escape peak of ⁇ -ray (6.13 MeV) of N-16 which is a radionuclide contained in the steam in the main steam pipe, to output a digital pulse, and measures a count rate of the digital pulse, and monitors a change in the count rate.
  • a radiation detector which is disposed close to a main steam pipe and detects a radiation to output an analog voltage pulse
  • a count-rate measurement unit which receives the analog voltage pulse, discriminates the analog voltage pulse entering a high-energy window which is set to contain a photoelectric peak, a single-escape peak, and a double-escape peak of ⁇ -ray (6.13 MeV) of N-16
  • the count-rate measurement unit of the sensitive main steam pipe monitor counts digital pulses which are discriminated by pulse heights, and acquires and outputs a count rate by performing a time constant process using software so that a standard deviation becomes constant based on the counted value. It is also possible to have a suitable response according to the purpose, by switching the standard deviation according to the count rate. If necessary, the plurality of count rates can be acquired by performing the plurality of time constant processes, and the plurality of count rates having different standard deviations can be displayed for comparison (for example, see PTL 1).
  • the steam in the main steam pipe is in a secondary system and does not contain artificial radionuclides in a normal state.
  • a background count rate in a normal state is low as approximately several cpm because cosmic radiations are dominant, and the background count rate and an alert setting point are close to each other. Accordingly, when alert transmission is attempted at high precision by preventing erroneous alerts, the standard deviation is reduced, and as a result, the response of the alert transmission is delayed, and when the standard deviation is increased by giving priority to the response of the alert transmission, erroneous alerts may frequently occur. Therefore, the alert is divided into two stages which are a caution alert and a high-level alert which is at an upper level of the caution level. The caution alert is transmitted during a stage of a slight leakage, and investigation is minutely performed by including a possibility of the erroneous alerts.
  • the radiation monitor of the related art is configured as described above. Since the analog voltage pulse from the radiation detector is input to the count-rate measurement unit, the pulse height values entering the set window are discriminated and counted, the time constant process is performed us ing software so that the standard deviation becomes constant based on the counted value, the count rate is acquired and output by giving priority to the responsiveness, and the alert setting point is close to the background count rate, the alert may be erroneously transmitted due to a statistical change, so-called fluctuation, of the count rate, and it is necessary to perform an operation of performing off-line inspection of an apparatus, to be safe, to confirm soundness, even when the count rate is restored to the background count rate.
  • the background count rate is small as a several cpm, and accordingly, a possibility that increasing tendencies become the same, cannot be ignored, and there is no fundamental resolution disclosed.
  • the present invention has been made to address the aforementioned problems and to provide a radiation monitor having high reliability and excellent maintainability which accurately determines whether or not fluctuation is a reason by online self-diagnosis with respect to transmission of a caution alert and provides information regarding the result.
  • a radiation monitor including: a radiation detector which detects a ⁇ ray emitted from a measurement target nuclide and outputs an analog voltage pulse; and
  • a radiation measuring instrument which receives the analog voltage pulse output from the radiation detector, and measures and outputs radiation in a measurement energy range
  • the radiation measuring instrument includes a pulse amplifier which amplifies the input analog voltage pulse and removes superimposed high frequency noise
  • a high-energy count-rate measuring instrument which discriminates the analog voltage pulse output from the pulse amplifier by a high-energy window and a low-energy window which are set so as not to be superimposed on each other in accordance with a voltage level, respectively, measures and outputs a high-energy count rate by performing a time constant process of the pulses entering the high-energy window so that a standard deviation becomes constant, and outputs an alert, when the high-energy count rate is increased beyond an acceptable set value
  • a low-energy count-rate measuring instrument which measures and outputs a low-energy count rate by moving and averaging the pulse entering the low-energy window at a constant measurement time
  • an alert-diagnosis device which determines whether or not the low-energy count rate is in a set acceptable range, when an alert is output from the high-energy count-rate-measuring instrument, determines that the alert is caused by fluctuation, when the low-energy count rate is in the acceptable range, determines that the alert is caused by any one of an increase in the ⁇ ray which is a measurement target or enter of noise, when the low-energy count rate increases beyond the acceptable range, and outputs a result of the determination, and
  • a display/user-operation device which displays each output and performs operations and settings of each unit.
  • the radiation monitor according to the invention is provided to automatically determine and display whether the alert is caused by the fluctuation or other matters, and therefore, a radiation monitor having high reliability and maintainability in which the time necessary for investigation of the causes of the alert transmission is significantly shortened, is obtained.
  • FIG. 1 is a diagram showing a configuration of a radiation monitor according to Embodiment 1 of the invention.
  • FIG. 2A is a diagram showing windows and spectra of the radiation monitor according to Embodiment 1 of the invention.
  • FIG. 2B is a diagram showing windows and spectra of the radiation monitor according to Embodiment 1 of the invention.
  • FIG. 2C is a diagram showing windows and spectra of the radiation monitor according to Embodiment 1 of the invention.
  • FIG. 3 is a diagram showing a flow of determination of a radiation monitor according to Embodiment 2 of the invention.
  • FIG. 4 is a diagram showing a configuration of a radiation monitor according to Embodiment 3 of the invention.
  • FIG. 5 is a diagram showing a configuration of a radiation monitor according to Embodiment 4 of the invention.
  • FIG. 6 is a diagram showing a relationship between a low-energy window and rare gas energy of the radiation monitor according to Embodiment 4 of the invention.
  • FIG. 1 is a diagram showing a configuration of a radiation monitor according to Embodiment 1 of the invention.
  • a radiation detector 1 which is radiation detecting means, detects a ⁇ ray emitted from N-16 nuclide which is a measurement target nuclide and outputs an analog voltage pulse.
  • a radiation measurement unit 2 which is radiation measurement means, includes a pulse amplifier 21 which is pulse amplification means, a high-energy count-rate-measurement functional unit 22 a which is high-energy count-rate-measurement means, a low-energy count-rate-measurement functional unit 23 which is low-energy count-rate-measurement means, an alert-diagnosis functional unit 24 which is alert-diagnosis means, an interface functional unit 25 , and a display/user-operation put unit 26 which is display/user-operation means.
  • the pulse amplifier 21 receives and amplifies the analog voltage pulse output from the radiation detector 1 and removes superimposed high-frequency noise and outputs the pulse.
  • the high-energy count-rate-measurement functional unit 22 a includes a high-window pulse-height discriminator 221 , a high counter 222 , and a high-energy count-rate-operation functional unit 223 a , the high-window pulse-height discriminator 221 receives the analog voltage pulse output from the pulse amplifier 21 and discriminates the pulse entering the window having the set high energy to output a digital pulse, and the high counter 222 counts the digital pulse at fixed cycle and outputs a counted value.
  • the high-energy count-rate-operation functional unit 223 a receives the counted value, operates and outputs a high-energy count rate by performing a time constant process so that the standard deviation is constant, and outputs an alert when the high-energy count rate increases beyond an acceptable set value.
  • the low-energy count-rate-measurement functional unit 23 includes a low-window pulse-height discriminator 231 , a low counter 232 , and a low-energy count-rate-operation functional unit 233 , the low-window pulse-height discriminator 231 receives the analog voltage pulse output from the pulse amplifier 21 and discriminates the pulse entering the window having the set low energy to output a digital pulse, and the low counter 232 counts the digital pulse at fixed cycle and outputs a counted value.
  • the low-energy count-rate-operation functional unit 233 receives the counted value and operates and outputs a low-energy count rate by performing a moving average operation for a constant measurement time.
  • the high counter 222 and the low counter 232 repeatedly perform set/reset for each set time, that is, fixed cycle (operation cycle) and count input pulses for a period of the fixed cycle to output a counted value.
  • the alert-diagnosis functional unit 24 receives an alert from the high-energy count-rate-measurement functional unit 22 a , receives the low-energy count rate from the low-energy count-rate-measurement functional unit 23 , and determines whether or not the low-energy count rate is in a set acceptable range by performing synchronizing with alert transmission. When the low-energy count rate is in the set acceptable range, the alert-diagnosis functional unit determines that the alert is caused by fluctuation, and when the low-energy count rate increases beyond the acceptable range, the alert-diagnosis functional unit determines that the alert is caused by any of an increase in the ⁇ ray which is a measurement target or enter of noise, and outputs results of the determination.
  • the interface functional unit 25 receives the high-energy count rate and the alert from the high-energy count-rate-measurement functional unit 22 a and results of the determination from the alert-diagnosis functional unit 24 , and outputs the items in a determined order, and the display/user-operation unit 26 receives and displays each output from the interface functional unit 25 and performs operations and setting of the radiation measurement unit 2 .
  • the low-energy count rate is also input to the interface functional unit 25 from the low-energy count-rate-measurement functional unit 23 .
  • FIGS. 2A to 2C are diagrams showing windows and spectra of the radiation monitor according to Embodiment 1, and illustrate spectra observed when observation is performed by connecting a provisional multi-channel pulse height analyzer to an output of the pulse amplifier 21 in the sensitive main steam pipe monitor.
  • the energy of the horizontal axis indicates pulse height values of a pulse wave pattern.
  • FIG. 2A is a diagram schematically showing energy spectra in a normal state
  • a reference numeral a in FIG. 2A indicates background spectra
  • a reference numeral NL indicates a low window
  • a reference numeral NH indicates a high window
  • FIG. 2B schematically shows energy spectra at the time of enter of noise and a reference numeral b indicates energy spectra in which noise spectra are superimposed on the background spectra a when electrostatic discharge light is generated in the radiation detector 1 .
  • FIG. 2B schematically shows energy spectra at the time of enter of noise
  • a reference numeral b indicates energy spectra in which noise spectra are superimposed on the background spectra a when electrostatic discharge light is generated in the radiation detector 1 .
  • FIG. 2B schematically shows energy spectra at the time of enter of noise
  • a reference numeral b indicates energy spectra in which noise spectra are superimposed on the background spectra a when electrostatic discharge light is generated
  • 2C schematically shows energy spectra when coolant is leaked from the steam generator (SG) and radioactivity is increased and a reference c indicates spectra when a count rate of the high-energy count-rate-operation functional unit 223 a is increased due to the N-16 nuclide.
  • the alert setting point is approximately 10 cpm which slightly exceeds the alert setting level, the peak in the high-energy window NH is not clear.
  • a ratio between the low-energy count rate of the low-energy window NL and the high-energy count rate of the high-energy window NH is great and the low-energy count rate is several hundred times of the high-energy count rate.
  • the low-energy count rate of the low-energy window NL and the high-energy count rate of the high-energy window NH are synchronously increased, and a ratio of the increased amounts (net weights) of the respective count rates is great and the low-energy count rate is several ten times of the high-energy count rate.
  • a reference numeral X indicates an amount of noise spectra which are superimposed on spectra in a normal state.
  • the ⁇ ray (6.13 MeV) from the N-16 nuclide is detected, and accordingly, the high-energy count-rate-measurement functional unit 22 a counts a photoelectric peak, a single-escape peak, and a double-escape peak of the ⁇ ray which is a measurement target nuclide, as shown with a reference numeral Yin FIG. 2C , and the high-energy count rate of the high-energy window NH is increased.
  • the low-energy count-rate-measurement functional unit 23 counts Compton scattering of the ⁇ ray from the N-16 nuclide as shown with a reference numeral Z in FIG. 2C , the low-energy count rate of the low-energy window NL increases, but a ratio of the respective increased amount is approximately 9.
  • a count rate m output by the high-energy count-rate-operation functional unit 223 a is acquired for each fixed cycle by the following Expressions (1) to (5), when the standard deviation thereof is represented as ⁇ , the time constant is represented as ⁇ , the counted value is represented as M, the fixed cycle time is represented as ⁇ T, a value of the previous operation cycle is represented as (previous time), and a value of the current operation cycle is represented as (current time).
  • a value of the previous operation cycle is represented as (previous time) and a value of the current operation cycle is represented as (current time).
  • the count rate m output from the high-energy count-rate-operation functional unit 223 a is controlled so that the standard deviation ⁇ is constant and the time constant ⁇ is in inverse proportion to the count rate m. It is possible to ensure desired precision by setting the standard deviation ⁇ constant.
  • a count rate n output from the low-energy count-rate-operation functional unit 233 is acquired for each fixed cycle by the following Expression (6), by setting the following.
  • ⁇ (BG) time constant corresponding to the background count rate m, and it is calculated from Expression (2) based on an average value m (BG) of the count value m for a long time, for example, 24 hours in a normal state
  • n ⁇ N/ ⁇ 2 ⁇ ( BG ) ⁇ (6)
  • the sensitive main steam pipe monitor which senses leakage occurring from the primary coolant to the secondary coolant of the steam generator (SG) by monitoring a change of the N-16 nuclide by setting the N-16 nuclide as a measurement target, mainly monitors a change thereof from the background count value and can perform the measurement by matching measurement times of the high-energy count rate and the low-energy count rate in the background state, by setting the moving average cumulative time T as 2 ⁇ (BG).
  • the count rate m in the background state is 5 cpm
  • n is 2,000 cpm
  • ⁇ (BG) is acquired as 10 minutes from Expression (2), and therefore, 2 ⁇ (BG) becomes 20 minutes.
  • the moving average cumulative time T is 20 minutes
  • the cumulative count value is 40000 counts
  • the value is 10 cpm.
  • the high-energy count rate is increased, the alert is transmitted from the high-energy count-rate-measurement functional unit 22 a , and the alert-diagnosis functional unit 24 determines whether or not the low-energy count rate is increased beyond the set acceptable range.
  • the low-energy count rate is in the set acceptable range and the alert is caused by the fluctuation
  • An alert occurrence frequency due to fluctuation can be calculated, evaluated, and determined, by setting a relationship between the moving average cumulative time T and the time constant ⁇ as l ⁇ T ⁇ 3 ⁇ with differences of the high-energy count rate m, the low-energy count rate n, and the net increase ratio k.
  • the alert transmission is generally caused by the statistical fluctuation according to the radiation measurement from the past experiments, and accordingly, when it is determined that the alert is caused by the fluctuation with this primary classification, the confirmation of the soundness of the apparatus to be safe, that is, on-line investigation performed by connecting a measurement device such as a provisional digital oscilloscope and multi-channel pulse height analyzer to the output of the pulse amplifier 21 and off-line investigation performed by check radiation source emission become unnecessary.
  • the high-energy count-rate-measurement functional unit 22 a counts the pulses entering the high-energy window NH which is set to contain a photoelectric peak, a single-escape peak, and a double-escape peak of the ⁇ -ray (6.13 MeV) which is the N-16 nuclide, and measures the high-energy count rate by performing a time constant process so that the standard deviation is constant.
  • the low-energy count-rate-measurement functional unit 23 counts Compton scattering of the ⁇ ray (6.13 MeV) which is the N-16 nuclide entering the low-energy window NL, and measures the low-energy constant rate by performing a moving average operation of the high-energy count rate for a constant measurement time which is double the time constant in a background state.
  • the alert-diagnosis functional unit 24 determines whether or not the low-energy count rate is increased beyond the set acceptable range and determines that the alert is caused by the fluctuation, when the low-energy count rate is in the set acceptable range. Therefore, a radiation monitor having high reliability and maintainability which can shorten the total time of a year necessary for investigation of the cause of the alert transmission with this primary classification is obtained.
  • the alert-diagnosis functional unit 24 identifies the statistical fluctuation of the radiation measurement which is the general cause of the alert transmission and other causes and outputs the results thereof, but in Embodiment 2, the alert-diagnosis functional unit 24 outputs the results thereof by performing secondary classification, in addition to this primary classification.
  • FIG. 3 is a diagram showing a flow of determination of a radiation monitor according to Embodiment 2 of the invention.
  • FIG. 3 shows a case where a noise diagnosis is added as the secondary classification of Embodiment 2 to the fluctuation diagnosis of Embodiment 1 as the primary classification.
  • “n ⁇ (1+p ⁇ ) ⁇ n (BG)?” in Step S 3 indicates determination of fluctuation diagnosis
  • n (BG) indicates an average value of the count rates n measured for a long time
  • p indicates a ratio of a spread of the standard deviation, and as described in Embodiment 1, when the standard deviation is set as 4.5, for example, the possibility of the erroneous determination becomes sufficiently low so as to be ignored.
  • the configuration of the radiation monitor is the same as that in FIG. 1 and will be described with reference to FIG. 1 .
  • the alert-diagnosis functional unit 24 receives the high-energy count rate m and the alert from the high-energy count-rate-measurement functional unit 22 a and receives the low-energy count rate n from the low-energy count-rate-measurement functional unit 23 in Step S 1 .
  • Step S 2 It is determined whether or not the alert is transmitted in Step S 2 .
  • the process returns to Step S 1 , and when the result is YES, a process in Step S 3 as the noise diagnosis is executed and it is determined whether or not the low-energy count rate n satisfies a relationship of n ⁇ (1+p ⁇ ) ⁇ n (BG).
  • Step S 3 it is determined that the alert is caused by the “fluctuation” in Step S 4 and the result of the determination is output in Step S 9 .
  • Step S 3 a low-energy count rate increased amount ⁇ n and a high-energy count rate increased amount ⁇ m are acquired and a ratio ⁇ n/ ⁇ m thereof is further acquired in Step S 5 .
  • Step S 6 it is determined whether or not a relationship of ⁇ n/ ⁇ m ⁇ r is satisfied as the noise diagnosis.
  • the result thereof is YES
  • it is determined that the alert is caused by the “enter of noise” in Step S 7 and the result of the determination is output in Step S 9 .
  • the result of the determination is NO in Step S 6
  • it is determined that the alert is caused by the “increase in measurement target radiation” in Step S 8 and the result of the determination is output in Step S 9 .
  • the determination is output and the diagnosis is held, but the diagnosis is resumed by resetting the alert, for example.
  • the high counter 222 counts the digital pulses output from the high-window pulse-height discriminator 221 and the high-energy count-rate-operation functional unit 223 a operates and outputs the high-energy count rate by performing the time constant process so that the standard deviation is constant, based on the counted value, but in Embodiment 3, a radiation monitor for expecting high precision is obtained with a configuration of using an up-down counter, instead of the high counter.
  • FIG. 4 is a diagram showing a configuration of the radiation monitor according to Embodiment 3 of the invention.
  • a high-energy count-rate-measurement functional unit 22 b of the radiation monitor according to Embodiment 3 includes the high-window pulse-height discriminator 221 , a high integration unit 224 , and a high-energy count-rate-operation functional unit 223 b
  • the high integration unit 224 includes an up-down counter 2241 , a negative feedback pulse generation circuit 2242 , and an integration control circuit 2243 .
  • the high-window pulse-height discriminator 221 receives the analog voltage pulse output from the pulse amplifier 21 and discriminates the pulse entering the window having the set high energy to output a digital pulse
  • the up-down counter 2241 receives the digital pulse output from the high-window pulse-height discriminator 221 through an up input
  • the negative feedback pulse generation circuit 2242 generates a feedback pulse at a repetition frequency so as to respond the output of the up-down counter 2241 with a primary delay of the time constant and inputs the feedback pulse to a down input of the up-down counter 2241 .
  • the up-down counter 2241 includes the up input and the down input, in which the up input proceeds the counting and the down input restores the counting process and outputs an addition and subtraction integration value as a result of addition and subtraction.
  • a signal pulse of a detector line which is the same as that of the high counter of Embodiment 1 is input to the up input, the negative feedback pulse is input to the down input, and addition and subtraction integration is performed consecutively without resetting. Therefore, the repetition frequency of the feedback pulse responding at the time constant with a primary delay is in equilibrium with respect to the repetition frequency of the input pulse, the inputs are switched to each other with an addition and subtraction integrated value in this state, and a stabilized state is obtained with oscillation for only a weighed amount of 1 pulse.
  • the integration control circuit 2243 performs weighing when the up-down counter 2241 performs the counting in accordance to the standard deviation of the count rate, and the high-energy count-rate-operation functional unit 223 b operates the count rate m by the following Expressions (7) to (9) so that the standard deviation ⁇ is constant based on the addition and subtraction integrated value Q of the up-down counter 2241 .
  • the negative feedback pulse generation circuit 2242 generates the feedback pulse based on the addition and subtraction integrated value Q.
  • ⁇ , ⁇ , and ⁇ are constants.
  • the addition and subtraction integrated value Q (current time) when ⁇ is 11 responds by an increase or a decrease of 1 count with respect to the input of 1 count
  • the addition and subtraction integrated value Q (current time) when ⁇ is 2 and ⁇ is 9 responds an increase or a decrease of 4 counts with respect to the input of 1 count
  • the addition and subtraction integrated value Q (current time) when ⁇ is 4 and ⁇ is 7 responds an increase or a decrease of 16 counts with respect to the input of 1 count
  • the addition and subtraction integrated value Q (current time) when ⁇ is 6 and ⁇ is 5 responds an increase or a decrease of 64 counts with respect to the input of 1 count.
  • the response time t (current time) depends on the weighing of the counts with respect to the input of the up-down counter 2241 .
  • the other configurations and operations are the same as those in Embodiment 1 and therefore, the overlapped description will be omitted by setting the same reference numerals.
  • the high counter 222 of the radiation monitor according to Embodiment 1 generates loss time according to the resetting, however, the up-down counter 2241 of the radiation monitor according to Embodiment 3 does not need the resetting and consecutively performs adding and subtraction integration, and therefore, it is possible to expect excellent linearity, that is, high precision, to the point of the high count rate.
  • the radiation measurement unit 2 performs the fluctuation diagnosis based on the low count rate, and in Embodiment 2, in the same manner, the radiation measurement unit 2 performs the fluctuation diagnosis and the noise enter diagnosis based on the low count rate. As shown in FIG.
  • the radiation measurement unit is configured with a high-energy radiation measurement unit 3 which is first radiation measurement means and a low-energy radiation measurement unit 4 which is second radiation measurement means, the analog voltage pulses output from the radiation detector 1 are respectively input to the high-energy radiation measurement unit 3 and the low-energy radiation measurement unit 4 , and the high-energy radiation measurement unit 3 operates in the same manner as the high-energy count-rate-measurement functional unit 22 a of Embodiment 1 or the high-energy count-rate-measurement functional unit 22 b of Embodiment 3, to output the high-energy count rate and the alert.
  • the low-energy radiation measurement unit 4 operates in the same manner as the high-energy radiation measurement unit 3 and outputs the low-energy count rate, with a configuration in which the high-window pulse-height discriminator 221 of the high-energy count-rate-measurement functional unit 22 a of Embodiment 1 or the high-energy count-rate-measurement functional unit 22 b of Embodiment 3 is switched with the low-window pulse-height discriminator 231 .
  • the low-energy radiation measurement unit 4 has a function of the transmission of the alert, if necessary.
  • the measurement energy range of the low-energy radiation measurement unit 4 is set so as to contain peak spectra of radioactive rare gas which is an emission management target and main Compton scattering spectra, as shown in FIG. 6 . Accordingly, in the standard deviation ⁇ in Expression (1), when the ratio of the standard deviation of the low-energy radiation measurement unit 4 to the high-energy radiation measurement unit 3 is set as 1 ⁇ 4, for example, in a case where the standard deviation of the high-energy constant rate is 0.1, the standard deviation of the low-energy constant rate becomes 0.025.
  • the time constant of the high-energy count rate is 10 minutes and the time constant of the low-energy count rate is 0.4 minutes from Expression (2), and it is possible to expect emission of radioactive rare gas in a preferred state with a balance between the fluctuation and the response.
  • a diagnosis apparatus 5 shown in FIG. 5 includes an alert diagnosis unit 51 and a display unit 52 , and receives high-energy count rate and the alert from the high-energy radiation measurement unit 3 and the low-energy count rate from the low-energy radiation measurement unit 4 .
  • the alert diagnosis unit 51 includes a fluctuation diagnosis functional unit 511 and a noise diagnosis functional unit 512 , operates in the same manner as the alert-diagnosis functional unit 24 of Embodiment 1 or Embodiment 2, outputs a result of the fluctuation diagnosis from the fluctuation diagnosis functional unit 511 , and outputs a result of the noise enter diagnosis from the noise diagnosis functional unit 512 .
  • the display unit 52 simultaneously displays the result of diagnosis of the alert diagnosis unit 51 and the trend of the high-energy count rate and the low-energy count rate.
  • a horizontal axis indicates the time
  • a left part of a vertical axis shows the high-energy count rate
  • a right part thereof shows the moving average value of the low-energy count rate in the screen
  • linear and logarithm can be desirably selected as scales thereof and the displaying is set so as to be performed by expanding or contracting the range, and accordingly, it is possible to determine the cause of the indication increase visually.
  • FIG. 6 shows a relationship between the low-energy window and the energy of radiation of the rare gas nuclide and a positional relationship with the high-energy window, and accordingly, in FIG.
  • Xe-135, Ar-41, Kr-85, Kr-87, and Kr-88 indicate rare gas nuclides
  • Y1, Y2, and Y3 respectively shows a double-escape peak, a single-escape peak, and a photoelectric peak of the N-16 nuclide.
  • the low-energy count rate has a range with a low concentration of released radioactivity by the radiation monitor of the invention and has a range with a high concentration thereof by another radiation monitor, and may be displayed as a dose equivalent rate, for example, for matching the units of the measured values of the low range and the high range.
  • the diagnosis apparatus 5 may be integrated with a calculator system of the plant.
  • Embodiment 1 to Embodiment 4 of the invention have been described, but the invention is not limited to those embodiments, and each embodiment can be freely combined with each other or modifications and omissions of the embodiments can be suitably performed within a scope of the invention.

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  • High Energy & Nuclear Physics (AREA)
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  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Molecular Biology (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Measurement Of Radiation (AREA)
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US20180038965A1 (en) * 2016-08-05 2018-02-08 Mitsubishi Electric Corporation Radiation monitoring equipment

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KR101975787B1 (ko) * 2016-12-02 2019-05-09 한국원자력연구원 방사성 핵종을 검출하는 방법, 이를 이용한 방사성 핵종 검출공정, 및 이를 위한 방사선 검출장치
WO2020118533A1 (fr) * 2018-12-11 2020-06-18 中广核工程有限公司 Procédé d'alarme de surveillance de fuite de centrale nucléaire et système d'alarme
CN111679312A (zh) * 2020-06-21 2020-09-18 陕西卫峰核电子有限公司 一种n-16辐射监测仪稳谱方法
JP7499734B2 (ja) 2021-06-01 2024-06-14 三菱電機株式会社 放射線モニタ
CN114675320B (zh) * 2022-03-28 2023-04-28 成都理工大学 一种混合β能谱的解谱方法、系统及存储介质

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US20160252626A1 (en) 2016-09-01
JP6072977B2 (ja) 2017-02-01
JPWO2015145716A1 (ja) 2017-04-13
EP3125000A1 (fr) 2017-02-01
EP3125000B1 (fr) 2019-10-16
WO2015145716A1 (fr) 2015-10-01

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